In a coating product spraying installation, it is known to spray the product by means of a rotary element called a bowl or dish, supplied with product and rotating at a speed included between 2,000 and 100,000 rpm. At the speeds in question, the bowl must be as light and balanced as possible in order to avoid unbalance to a maximum, particularly if its drive means comprise an air and/or magnetic bearing turbine.
It is known, for example from WO-A-94/12286, to connect a bowl to a rotor by means of a fitting ring capable of radial expansion. It is also known, for is example from WO-A-01/62396 or from U.S. Pat. No. 4,473,188, to use magnetic coupling means between a bowl and the rotor of a turbine. In these devices, the effort to be exerted in order to uncouple the bowl from the rotor must be intense. As soon as these elements are separated, the effort of magnetic coupling decreases very considerably, with the result that nothing opposes the movement of tearing-away of the bowl. This results in a risk of a bowl escaping the operator during its dismantling, as the resistant effort of the magnetic coupling drops very rapidly as soon as the bowl is separated from the rotor.
Now, if such a bowl falls, its spraying edge is generally damaged, this degrading the quality of the spray obtained. In other words, when a bowl falls on the ground, it is not rare to have to replace it, while such equipment is expensive in view of the care taken to manufacture it. Known devices comprise one or more magnets constituting together an annular magnetization device. This involves this or these magnets being sufficiently voluminous to generate an intense magnetic field, which is detrimental to the compactness of the sprayer. In addition, the weight and inertia of the bowl are relatively great, more particularly in the case of the bowl bearing the permanent magnet or magnets. Finally, the magnets must be subjected to a particular mechanical assembly in order not to risk bursting under the effect of the centrifugal efforts.
It is a more particular object of the present invention to overcome these drawbacks by proposing a spraying bowl which may be easily driven by a rotor provided to that end, thanks to an efficient magnetic coupling, while allowing an easy assembly and dismantling of the bowl, at the beginning and end of service.